Tapering a straight barrel.

B

Bnhpr

Ben Hooper
Besides the obvious "buy a pre-tapered barrel"

Can anyone give me some pointers on tapering my 1.250 straight barrel in HV taper?

The only idea I have now is to offset the tail stock appropriate distance toward me so the diameter is .900 at 29 inches, and does not touch 5 inches from the bolt face. And chase the tool with the follower rest?

Any other ideas, I do not have a taper attachment by the way.

Ben
 
I recently got my first experience with a lathe doing this very task. Didn't use the follower, though it wouldn't have hurt.
My experience: The barrel started life as a 54 Match Anschutz (1.040 turned down to .75 at the muzzle, 22 inches of taper). The number of passes required resulted in tooling needing replacement or grinding before getting to the final pass to produce a surface ready for polishing. Turned at 50 RPM to prevent any heat from causing the barrel to "bend" (no personal experience of this happening to a barrel, just makes sense to me).
The result? Too many variables need to be eliminated (still waiting for the stock, find the right scope/ammo/trigger, etc..), but the second 100 yd 5 shot group shot (from a slave stock) in slightly windy conditions (5-10 mph, shifting from 7 to 10 o'clock) went into 1 1/8 inch with Ely Sub sonic.
I'd be interested in hearing the details of your experience.
Good luck.
 
Bnhpr said:
Besides the obvious "buy a pre-tapered barrel"

Can anyone give me some pointers on tapering my 1.250 straight barrel in HV taper?

The only idea I have now is to offset the tail stock appropriate distance toward me so the diameter is .900 at 29 inches, and does not touch 5 inches from the bolt face. And chase the tool with the follower rest?

Any other ideas, I do not have a taper attachment by the way.

Ben
Click to expand...
Ben, remember, when you swing the workpiece out this much from true rotational center, you will need to put the workpiece between centers and drive it with a lathe dog......but you probably knew that.
 
And, a follow rest won't work on a taper or offset. You are better off setting the offset on the tailstock and using the steadyrest about half way down the barrel and moving it for the remainder. Lots of work, I've done it but can't imagine doing it again.
 
I had a crazy idea of trying to ajust the follower rest as I moved up the barrel.

Probably as stupid as thinking I can back out the compound rest as I cut. That always ends in tears too.

The steady rest is probably the best option. steel tool, ground with a high helix angle, and low feed rate, lots of cooling.

How about if I cut the taper with the compound rest, staged, with the follower rest, ahead of my cut? (set the tool up as far right as possible)

Ben
 
Unless you are just bound and determined to do it yourself, why not just send it back to the barrel maker and pay them to do it? Surely is easier.
 
Don Nielson said:
And the big thing is the bore will probably be larger at the front after you get done. Don
Click to expand...
Don, surprisingly, the bore does not open up all the time. A few years ago I had 2 Lilja barrels I wanted to taper (from 1.25 straight). I called Dan Lilja and he said that if I used a positive rake HHS tool and shallow depth of cut (about 0.04"/side) and a fast enough feedrate to stay ahead of the heat the bore wouldn't change. (I used 0.007" IPR)

I slugged the bores before and after and could not detect any change in bore size. Now, had I used a neutral or negative rake carbide my guess is they would have opened up.

Mickey has the best idea though.
 
taper

When I was an apprentice at a local plant, I tapered a few barrels for a gentleman.
He was/is a competitive shooter who visits these pages now and then.
He used to give his worn BR barrels to his friend Charlie(my lead-off) down the road and Charlie and I used to taper them for his sporter(hunting) rifles.

I have to ask, I have read in different threads here about moving the tailstock off to cut angles on barrels--- WHY??
I have tapered barrels and cut many angles on similar other things and in 30+ years have never moved a tailstock to do it.
Why complicate a simple machining operation and then have to re-indicate your tailstock back in??

One way to taper a barrel:
Chuck up the chamber end in 4 jaw or a good adjustable 6 jaw
Use a steady rest out near the muzzle end and after indicating, cut a nice center in the muzzle.
Put center in muzzle end and move steady rest back.
Turn compound to desired angle and start at muzzle end and taper to near desired dia. at muzzle---within about .005 or so.
Yes, you will run out of travel and have to make adjustments as you "step" the taper to completion ----no big deal--you should be able to "blend" the "steps" in perfectly.
The closer you get to the chuck the less you'll need the steady rest and after a few "steps" you'll be able to remove it.
When taper is complete use sandpaper to "blend" everything in.
It's pretty basic machining and doesn't take that long once you get going.
I would not complicate things by moving a tailstock around when it isn't necessary.

Rich
 
dipper said:
When I was an apprentice at a local plant, I tapered a few barrels for a gentleman.
He was/is a competitive shooter who visits these pages now and then.
He used to give his worn BR barrels to his friend Charlie(my lead-off) down the road and Charlie and I used to taper them for his sporter(hunting) rifles.

I have to ask, I have read in different threads here about moving the tailstock off to cut angles on barrels--- WHY??
I have tapered barrels and cut many angles on similar other things and in 30+ years have never moved a tailstock to do it.
Why complicate a simple machining operation and then have to re-indicate your tailstock back in??

One way to taper a barrel:
Chuck up the chamber end in 4 jaw or a good adjustable 6 jaw
Use a steady rest out near the muzzle end and after indicating, cut a nice center in the muzzle.
Put center in muzzle end and move steady rest back.
Turn compound to desired angle and start at muzzle end and taper to near desired dia. at muzzle---within about .005 or so.
Yes, you will run out of travel and have to make adjustments as you "step" the taper to completion ----no big deal--you should be able to "blend" the "steps" in perfectly.
The closer you get to the chuck the less you'll need the steady rest and after a few "steps" you'll be able to remove it.
When taper is complete use sandpaper to "blend" everything in.
It's pretty basic machining and doesn't take that long once you get going.
I would not complicate things by moving a tailstock around when it isn't necessary.

Rich
Click to expand...

Thank You Rich

That's how I usually turn short tapers (Morse, Jacobs etc.).

I'll just have to bay close attention to the steps, not to create a ridge or groove that I cannot file/sand out.

Ben
 
dipper said:
When I was an apprentice at a local plant, I tapered a few barrels for a gentleman.
He was/is a competitive shooter who visits these pages now and then.
He used to give his worn BR barrels to his friend Charlie(my lead-off) down the road and Charlie and I used to taper them for his sporter(hunting) rifles.

I have to ask, I have read in different threads here about moving the tailstock off to cut angles on barrels--- WHY??
I have tapered barrels and cut many angles on similar other things and in 30+ years have never moved a tailstock to do it.
Why complicate a simple machining operation and then have to re-indicate your tailstock back in??

One way to taper a barrel:
Chuck up the chamber end in 4 jaw or a good adjustable 6 jaw
Use a steady rest out near the muzzle end and after indicating, cut a nice center in the muzzle.
Put center in muzzle end and move steady rest back.
Turn compound to desired angle and start at muzzle end and taper to near desired dia. at muzzle---within about .005 or so.
Yes, you will run out of travel and have to make adjustments as you "step" the taper to completion ----no big deal--you should be able to "blend" the "steps" in perfectly.
The closer you get to the chuck the less you'll need the steady rest and after a few "steps" you'll be able to remove it.
When taper is complete use sandpaper to "blend" everything in.
It's pretty basic machining and doesn't take that long once you get going.
I would not complicate things by moving a tailstock around when it isn't necessary.

Rich
Click to expand...

Oh, I forgot to ask, do I need to face out the 60 degree center from the muzzle, or leave it in there? I do not expect any damage to it during the taper cut, using a live center.

Ben
 
Bnhpr said:
Oh, I forgot to ask, do I need to face out the 60 degree center from the muzzle, or leave it in there? I do not expect any damage to it during the taper cut, using a live center.

Ben
Click to expand...


Actually you need to cut 65-70 degree centers if you offset onto a 60 degree live center tool, or the lands of the rifling will be part of the bearing surface and eat up your fine live center surface finish like a grinder.......................Don
 
Don said:
Actually you need to cut 65-70 degree centers if you offset onto a 60 degree live center tool, or the lands of the rifling will be part of the bearing surface and eat up your fine live center surface finish like a grinder.......................Don
Click to expand...

I'm not going to offset the tailstock. I believe Rich's method is a preferred method of cutting a taper, since the work piece will be supported close to the tool, by the steady rest.

The taper will be cut in steps, using the compound rest, which I will adjust the wedge on appropriately for slack.

The angle of the rest can paralelled against a 24" piece of fishing line as a guide, between the point of the dead center, and The jaw of a 3 jaw chuck opened 1.25 inches.

I will have to make 2+ passes, since the cut will be too heavy at the muzzle, with a diameter change of 1.25 to.900 (-.350)

Unless someone has a better idea.

Ben
 
If you go with the steadyrest method you are going to be doing alot of hand cranking on the compound dial creating a very poor finish that will require alot of filing and sanding to clean up (as opposed to a power fed carriage cut), on top of juggling around the positioning of the steadyrest to gain full barrel length access.


Bnhpr said:
I'm not going to offset the tailstock. I believe Rich's method is a preferred method of cutting a taper, since the work piece will be supported close to the tool, by the steady rest.

The taper will be cut in steps, using the compound rest, which I will adjust the wedge on appropriately for slack.

The angle of the rest can paralelled against a 24" piece of fishing line as a guide, between the point of the dead center, and The jaw of a 3 jaw chuck opened 1.25 inches.

No, line would have to go to .450" from dead center point.

Use an existing tapered barrel positioned between centers to set your compound, just bring loosened compound hard up to barrel and tighten. If you dont have exact same taper do this procedure and tweek a little.

I will have to make 2+ passes, since the cut will be too heavy at the muzzle, with a diameter change of 1.25 to.900 (-.350)

Unless someone has a better idea.

Ben
Click to expand...
 
taper

You should only have to move the steady rest one time.
Yes, you need a little skill and knowledge to get a good finish with the toolbit before polishing---yes, there is a fair amount of hand turning of the compound----builds character!!!LOL

Rich
 
I don't know how many barrels I have tapered but it has been a bunch. I often use 1 1/4 inch blanks since I may have to contour specially anyway. I have recontoured barrels which were cut rifled, button rifled, and hammer forged. Stainless, chromoly, and carbon manganese. I have tapered or retapered most of the BR barrels I ever shot. Barrels which have been properly stress relieved don't warp and I've not seen one expand measurably. I've never had a barrel shoot worse after recontouring except where it was a HV barrel turned down to a lightweight hunting contour. It was not expected to shoot as well as a BR rifle and it didn't! But then, lightweight hunting rifles never do.
I have used taper attachments, a tracer setup, and offset the tailstock. All methods work fine but offsetting the tailstock does tend to create vibration which can lead to chatter. I seldom use a steady rest unless I'm having a lot of trouble with chatter on a slim barrel.
To set up the barrel to cut a taper using the tailstock offset method, first, mark the portion of the barrel you wish to taper. If you are working with a straight blank, it makes things easy. Set the barrel between centers with the breech end at the headstock. Mount a dial guage on the toolpost. If you are going to taper from .9 at the muzzle to 1.250 at 5" ahead of the breech on a 30 inch blank, you will start by setting the plunger against the muzzle end of the barrel and will offset the tailstock toward you .175" plus about .030" for a total of .205. Why the plus .030"? When you move the muzzle toward you by .175" the point 5" ahead of the breech will move in the same direction about 1/6 that amount so you have to compensate. After you have offset the tailstock, simply run the dial along the barrel. The difference between the indication at the muzzle and at the 5" mark should be .175" ([1.250-.900]/2). Adjust further if necessary so it is.
The tool should be a modified chipbreaker type ground with a very sharp edge. The trough behind the edge should be radiused about 1/16". A lead angle of about 15 degrees is fine. The resultant edge is a bit fragile but that's it will cut easily. Use a good cobalt HS steel. If the steel is easy to grind, it's easy to dull. In use the tool will be set about .015-.020 ABOVE center. The chip should come off in a nice curl (like a coil spring) and break off in 6 to 10 inch sections. Run about 350 RPM; slower if it chatters. Cut .030 -.050. Feed about .010 IPR. The cut, speed, and feed rate will vary according to the rigidity and power of the machine. Coolant is nice if you can.
Grease the ends of the barrel at the centers. Figure on cutting off 1/8" and recrowning.
I guess that's about it. Sometimes it's worth while to cut to within .010 of finished diameter, sharpen the tool, then take a .005" cut to finish.
Turning a 1 1/4 blank to a HV taper should present no problems. The barrel has sufficient rigidity that chatter shouldn't occur unless everything's wrong.
If you are turning with no coolant, you will have to loosen the tailstock quill off after the second pass or so and keep checking it as the job progresses.
If you have much machining experience, I've told you more than I needed to. As I said, turning to a fat taper should present no problems. Regards, Bill.
 
I agree with Mr Leeper,
I used a 2" boring head in the tailstock with a turned down #2MT center and offset the required amount. Found out it ran better with a centered bronze muzzle insert. The boring head was cheap and I didn't have to change my tailstock. Light cuts with sharp tooling near finish OD left a nice finish with no chatter. Cut the sharp taper at the breech end with the compound.
 
I'll add a comment also. I recently turned down a couple barrels and played with the feed and speeds a bit. I don't have coolant, and I don't like heating the barrel up either, so I just put my earplugs in and held the air nozzle over the toolpost and blasted the bit with air on each pass. The chips went from 6" stringy curls to perfect little C's, and the barrel was cool to the touch after each pass. I have a 60gal compressor and the air was around 90psi. I'll be using air again on any barrel I recontour unless I get a coolant setup.
 
Bill, How does this tool look for 4140? (see pic)

The far end I ground to thread to a shoulder (tenon)

My main concern is chatter and/or the barrel climbing the tool. It sounds like that may not be a problem with a 1.25x30 piece of 4140?

I may try the offset method, and should know quite soon if it will not work, then, I can go back to the compound rest if I have to.

Thanks everyone.

Ben
 

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